Almost every blind-measuring guide online was written for a window that does not exist in Kolkata. It assumes a deep timber reveal, a sash that slides upwards, no grille, and a wall you may drill anywhere you like. Follow one of those guides in a Bowbazar flat or a Salt Lake apartment and the blind arrives perfectly sized for a window you do not own.
The windows we actually measure here are aluminium sliders, steel and wooden casements that open inwards, and older frames set flush into thick brickwork. Nearly all of them sit behind an M.S. grille, most have a sunshade or a ventilator above, and a great many have a lock or handle standing proud of the frame. Every one of those details changes the number you write down. We have been measuring and fitting blinds across Kolkata since 1971, and the mistakes repeat themselves reliably enough to be worth setting out in order.
The one rule that prevents most mistakes
Measure the opening. Do not make the deduction yourself.
Every made-to-measure blind needs a small clearance so it can rise and fall without scraping the frame. The workshop applies that allowance, and it is not the same figure for every blind type. If you deduct half an inch for luck and the workshop deducts its own allowance on top, you end up with a blind an inch too narrow and daylight spilling down both sides. It is the commonest self-measuring error there is, and it is the one that cannot be undone — a blind cut short cannot be let out.
So write down the true opening in plain figures, state clearly whether it is an inside or an outside measurement, and leave the arithmetic to the people making it.
What you need before you start
A steel tape, not a tailor’s tape. A cloth tape sags across a six-foot drop and stretches with age; over a wide window it can be out by half an inch on its own, which is the whole tolerance gone before you have written anything down.
Beyond that: a step stool so you are level with the top of the window rather than squinting up at it, a pencil and paper, and measurements taken in inches to the nearest eighth. A small window is a one-person job. Anything above about five feet wide needs a second pair of hands, because a tape held at arm’s length droops in the middle and reads long.
One habit worth adopting immediately: measure every window separately, even the two in the same bedroom that look identical. In a building of any age they rarely are. Plaster thickness alone varies enough to matter, and two windows an inch apart in size will produce one blind that fits and one that binds.
Inside fit or outside fit: decide before you touch the tape
The trade uses several names for the same two things. Inside fit, reveal fit and recess fit all mean the blind sits within the window opening. Outside fit, wall fit and face fit all mean it mounts on the wall or the frame face and overlaps the opening. The choice is binary, and it changes every number that follows, so settle it first.
Inside fit looks neat, keeps the blind out of the room, and leaves a handsome frame visible. It also leaves a narrow light gap down each side, and it requires enough depth at the top of the opening for the headrail to sit in.
Outside fit blocks far more light, hides a frame that is ugly or out of square, and works where there is no usable depth at all. It uses more material and projects into the room a little.
In Kolkata, outside fit wins more often than the imported guides suggest, for three reasons. Reveals are frequently too shallow once a grille is in the way. Frames in older buildings are rarely square, and an inside-fit blind advertises every millimetre of that. And bedrooms in this city need daylight stopped at the edges rather than merely reduced, which an inside fit will never quite manage.
Step 1: check the depth before anything else
Depth decides whether inside fit is even available to you, so measure it before you measure anything else. Take it at the top of the opening, since that is where the headrail goes.
Measure from the front edge of the reveal back to the first thing that projects — and in Kolkata that is usually not the glass. It is the grille, the window lock, the handle, or the frame of a mosquito mesh. That obstruction, not the pane, sets your working depth.
As a rule of thumb, roller and zebra blinds need the least depth because the tube and brackets are compact. A wooden or Venetian headrail carrying a tilt mechanism needs the most. Honeycomb and Roman blinds fall between the two. The exact minimum varies by system, so the useful thing is to record the figure you measured and tell it to us, rather than deciding for yourself whether it will do.
Step 2: measure the width in three places
For an inside fit, measure the width of the opening at the top, the middle and the bottom, and record the narrowest of the three. Older Kolkata openings taper; a quarter to half an inch of difference over a six-foot window is ordinary, not a fault. A blind cut to the widest of the three figures will drop cleanly for two feet and then jam.
For an outside fit, you are not measuring the window at all — you are measuring the area you want covered. As a working figure, allow around two inches of overlap on each side of the opening and the same again above, provided there is solid wall there to fix into. Then look up and check what is actually in that space: a chhajja or sunshade, false-ceiling coving, the indoor unit of a split AC, or a curtain rod already in place.
Step 3: measure the drop in three places
For an inside fit, measure from the top of the opening down to the sill on the left, in the centre and on the right, and record the longest of the three so the blind covers the full opening.
For an outside fit, measure from the point where the headrail will sit down to where you want the blind to finish. Below the sill by a couple of inches is the usual choice, and it looks deliberate. Ending exactly level with the sill looks deliberate too. Ending an inch above it looks like an accident.
Sills here are worth a second look. A great many Kolkata windows have had a marble or granite sill added years after the building went up, and those are often neither level nor square to the frame. Measuring at one point only is how that gets missed.
The grille, the handle, and the rest of the obstacle course
This is the part no imported guide covers, and it is where most Kolkata orders go wrong.
The grille. If the M.S. grille sits inside the reveal, it usually rules out an inside fit for any slat blind, though a slim roller may still clear it. If the grille is fixed to the outer face of the opening, the reveal is yours and the normal rules apply. Check which you have before assuming anything.
Windows that open inwards. Common in older North and Central Kolkata flats, and a blind fitted inside the reveal makes the window unopenable. The answer is an outside fit mounted high and wide enough that the shutters swing clear beneath the headrail.
Sliding aluminium windows. Usually the easiest case, since the handle is recessed. The catch is the mosquito-mesh track, which eats depth you assumed you had.
Ventilators. The small hopper window above the main opening is a Kolkata fixture, and it is a decision point. If the blind stops below it, daylight pours through that gap all day, which is fine in a kitchen and unacceptable in a bedroom. If you want it covered, the blind must be mounted above it and sized accordingly.
Air conditioners and exhaust fans. A split indoor unit, its pipe chase, or a kitchen exhaust fan can each take away the bracket position you were counting on. Note them at measuring stage, not on installation day.
Wide windows: one blind or two
Past a certain width a single roller or Roman blind becomes heavy to operate and the tube can visibly sag across the middle. Beyond that point the sensible answers are two or three blinds sharing a common headrail, or vertical blinds, which handle width by design and suit balcony sliders particularly well.
If a window is going to be split, give us the total opening width and let the workshop calculate the division. Measuring two halves yourself and adding them together is how the joint ends up landing in the middle of the glass instead of over a mullion.
Settle the control side and the roll direction now
These are decided at measurement, not at installation, and changing them afterwards means new components.
Control side. Decide which end the chain or wand hangs from, and stand in the room to decide it. A chain that ends up behind a wardrobe, over a bed, or on the hinge side of a door is a daily irritation for years.
Roll direction, for roller and zebra blinds. A standard roll brings the fabric down the back of the tube, closer to the glass, giving the tightest light seal. A reverse roll brings it down the front, which is what clears a projecting handle, a deep sill or a grille — at the cost of a slightly larger light gap at the top.
If you are considering motorised blinds, raise it before measuring rather than after. The motor lives inside the tube, and the power point needs to be near the headrail — far easier to arrange while the room is still being worked on.
A quick reference by window type
| Window type | Usual fit | What to watch for |
| Aluminium sliding window, newer flats | Inside fit usually works | Measure depth to the mosquito-mesh frame, not to the glass |
| Casement opening inwards | Outside fit | Shutters must swing clear beneath the headrail |
| Grille set inside the reveal | Outside fit, or a slim roller if it clears | Depth is measured to the face of the grille |
| Grille on the outer face | Inside fit is open to you | Normal depth rules apply |
| Wide balcony slider | Vertical blind, or a split set | Give the total width and let the split be calculated |
| Window with a ventilator above | Outside fit, mounted above the ventilator | Otherwise daylight comes through the ventilator all day |
| Kitchen window over a counter | Inside-fit roller in a wipe-clean fabric | Keep the control chain well clear of the hob |
| Bay window | One blind per facet | Measure each facet on its own; the corner angles are never equal |
Write it down like this
One line per window, in the same order every time, so nothing is left to memory:
Room — which window — inside or outside fit — width — drop — depth — control side — blind type.
For example: Bedroom 2, left window, inside fit, 46½ wide, 58 drop, 3½ depth to grille, chain on right, zebra blind.
Then photograph each window with the tape held across it. It takes ten seconds, and it has settled more queries in our showroom than any amount of describing.
When to stop measuring and let us do it
Measuring your own windows is genuinely useful for planning a room and getting an estimate together, and it will make the showroom conversation far quicker. It is not the measurement the blind gets cut to.
Avikar’s in-home measurement is free, and our own team does the fitting. Hand the job over without hesitation if the frame is visibly out of square, if it is a bay, if there is a grille you are unsure about, if the blind is to be motorised, or if it is a commercial order — offices, hotels, schools and hospitals are work we take on in bulk, and institutional windows are almost never as standard as the drawings suggest.
There is a practical reason beyond convenience. Whoever takes the measurement carries responsibility for the fit. When our team measures, getting it right is our problem, not yours.
Frequently Asked Questions
Should I measure the window or the blind?
Measure the window opening. Blinds are made to the opening, not the other way round, and the maker converts your opening size into a finished blind size. Tell us the opening and say whether the blind is going inside the recess or on the wall outside it. Those two pieces of information are all we need to start.
Do I need to subtract anything from my measurement?
No, and this is the important one. The workshop applies the operating clearance, and the allowance differs between blind types. If you deduct as well, the deduction happens twice and the blind comes back too narrow. Give the exact opening figure.
Can I have blinds if my window has a grille?
Almost always, yes. What the grille changes is where the blind mounts. If the grille is fixed inside the window recess it usually eats the depth a headrail needs, so the blind goes on the wall outside the opening instead — which in a bedroom is often the better result anyway, because it stops light at the edges. If the grille is on the outer face of the window, the recess is unaffected and an inside fit is straightforward.
How much depth do I need to fit a blind inside the window?
It depends on the blind. Roller and zebra blinds have the most compact headrails and need the least; wooden and Venetian blinds carry a tilt mechanism and need the most; Roman and honeycomb sit in between. Rather than working to a number you have read somewhere, measure the depth from the front edge of the recess to the first thing that projects — grille, handle, or mesh frame — and tell us that figure. We will say immediately what will fit.
How much wider than the window should an outside-fit blind be?
About two inches of overlap on each side and the same above is the usual working figure, assuming there is solid wall to fix into. More overlap means better light control at the edges. Check first that the space above is clear of a sunshade, ceiling coving, an AC unit or an existing curtain rod.
My window opens inwards. Can I still have blinds?
Yes. The blind is mounted outside the opening, high enough and wide enough that the shutters swing freely underneath it. This is very common in older Central and North Kolkata flats and is a routine fitting for us — but it must be planned at measurement, because an inside fit on an inward-opening window will simply lock the window shut.
Can one blind cover a wide balcony window?
Past a certain width a single fabric blind becomes heavy to pull and the tube starts to sag in the middle. For balcony sliders we would normally suggest either vertical blinds, which are built for width, or a set of blinds sharing one headrail. Give us the total opening width and we will work out where the divisions should fall.
Do I still need to measure if Avikar is coming to the house?
Not for accuracy — our team takes the measurements the blinds are made to, and that visit is free. Rough figures are still worth having if you want an estimate before anyone visits, or if you are choosing fabrics in the showroom first and want to know roughly what each window will take.
Bring your measurements, or let us take them
Every blind we make is cut for one window and no other, which is exactly why the measurement matters more than the fabric. Come in with your figures and we will tell you what fits, or book the free in-home measurement and let our team take them properly. Avikar has been furnishing Kolkata homes since 1971, and more than 6,500 households across the city have bought from us.
Avikar Furniture & Furnishings
46 Central Avenue, Bowbazar, Kolkata, West Bengal 700012
Monday to Saturday, 10:30 AM to 7:00 PM. Sunday closed. Parking on request.
Call or WhatsApp 8080095551
See the full range on our blinds showroom page. If you are still deciding what to fit, start with our complete window blinds buying guide, then read up on roller blinds, Roman blinds, wooden blinds, zebra blinds and honeycomb blinds. Fitting curtains in the same room? Our guide to measuring for curtains works to a completely different set of rules.
